Production of large quantities of hiighly purified receptors is an underlying requirement for all the projects in ttie Program Project -Structure-Function of Opioid Receptors for Drug Discovery. The production of these samples will be carried out using well established protocols that have now been optimized for use with GPCRs as part of GPCR Network's GPCR Structure Determination Pipeline. These production protocols now include the use of newly developed GPCR fusion partner toolchest for stabilization and crystallization that has increased the quantity and quality of structures that we are able to determine. Most notably, with the use of a new fusion partner, apo-cytochrome b562 (RIL) mutant, BRIL, we were able to determine the structure of the A2A adenosine receptor- ZM241385 to 1.8 A resolution, the structure of NOP, and more recently 2 agonist bound serotonin receptors in an activated state. Structural studies will demand the use of large volumes of highly purified protein for crystallization studies while others doing functional studies will need much less. Studies that led to the structure solution of the K-opioid receptor and the nociceptin/oprhanin FQ peptide receptor required a large number of constructs and an average of 25 mgs of highly purified protein or about 100 liters of biomass. For receptor-ligand complex structural studies we estimate that 5-10 mgs will be required per structure.